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Computing Circuits
A.4.9
Inverting Integrator with Resistive Reset
This circuit differs from that shown in Figure A–27 because it yields a breakpoint rather
than a pure integration. On a log plot, the integrator slope is –6 dB per octave at the 0 frequency
intercept, and the 0 dB intercept occurs when f = 1/2πRC. A breakpoint plots flat
on a log plot until the breakpoint where it breaks down at –6 dB per octave. It is –3 dB when
f = 1/2πRC.
R F is in parallel with the integrating capacitor, C, so it is continually discharging C. The
low frequency attenuation that is the best attribute of the pure integrator is sacrificed for
the reset circuit complexity
V OUT
V IN1
R F
R G
1
R F
C 1
A–37
V IN
R G
+V CC
R
R F
C
+V CC
_
+
V OUT
Output Amplitude — dB
3
1
–1
–3
–5
–7
–9
–11
–13
–15
Phase
V OUT
190
180
170
160
150
140
130
120
110
100
Phase — Degrees
R
–17 90
10 100 1 k 10 k 100 k
f – Frequency – Hz
V IN = 1 Vp-p RG = RF = R = 10 k
V CC = 5 V
C = 0.01 F
Op Amp = TLV247x
Figure A–32. Inverting Integrator with Resistive Reset
A-32